NO　reduction　with　biomass　char　was　studied　from　considering　its　structural　properties.　Raman,　XPS　and　XRD　were　employed　to　characterize　the　char　structure.　Three　types　of　biomass　chars　were　used　for　NO　reduction　at　a　fixed　bed　reactor　in　NO/O2　at　900　.　The　results　showed　that　the　heat　treatment　led　to　an　obvious　reordering　of　structures　in　all　chars.　There　were　significant　differences　between　NO　and　O2　reaction　in　terms　of　the　char　structural　changes　in　aromatic　systems,　surface　groups　and　crystalline　developments.　New　O-containing　groups　were　formed　and　could　be　present　as　C-O　and　–COO　groups　in　both　the　NO　and　O2　reactions.　Two　different　pathways　for　char-NO　and　char-O2　reaction　were　given,　respectively.　It　is　proposed　that　the　reaction　channel　of　NO　would　be　blocked　as　carbon　molecular　was　firstly　surrounded　by　O2　during　NO/O2　reaction.　The　denitration　performance　of　biomass　char　should　be　linked　to　the　structural　features　of　char-HT　and　the　behaviors　of　char　structural　changes　in　the　subsequent　gasification　in　NO/O2.　©　2020　Elsevier　Ltd